From Winter To Spring This Week

The weather over the coming week will be a period of transition from the bitter winds and snows of winter to the warm winds and heavy rains of spring. After you finish complaining about the wintry start to the week, remember that parts of MA and CT are seeing 3-6″ of snow driven by 60-70 mph winds and accompanied by crashing thunder. We’re being cheated out of a fascinating event.

The Setup: This Evening

Evening Water Vapor Satellite Showing The Development Of A Strong And Dynamic Clipper Tonight/Tomorrow Morning. Image Credit: COD

An extremely potent disturbance is currently blasting SE across the Eastern Great Lakes. The impressive couplet of strong rising/sinking air indicates this is an extremely strong disturbance. Arctic air is already pouring in behind this storm with winds across the Midwest gusting over 50mph this afternoon. This whole system is moving east quite quickly and will be in New England tomorrow morning. Also going on this evening is the development of an offshore wave embedded in the subtropical moisture feed. This will drag the moisture offshore which is why the arctic disturbance won’t bring us a blockbuster storm.

The RGEM model is showing what the storm will look like when it’s over our area tomorrow at 8 AM. Most southern areas will see at least a few flakes and York County could see a couple inches. Most just get a dusting if that. The mountains look to remain completely dry. The bulk of this one will be in Southern New England where the higher elevations of eastern CT and MA will see up to 6″ of snow, hurricane force wind gusts, and thundersnow. For those areas, this will be a pretty crazy storm. For everyone, the storm moves quite quickly and is gone by tomorrow afternoon.

High Winds: Tomorrow All Day

12Z GFS Showing Wind Potential Tomorrow.

One impact that the mountains and the coast alike will feel will be the winds. Winds under the yellow line are eligible to take a hike to the surface. It is hard to see here but the GFS does have a 50kt contour in the blue circled area Sunday morning for Portland. A good rule of thumb I learned from CBS 13 meteorologist Charlie Lopresti is to take whatever the model puts out for knots in the mixing layer and forecast the same value in mph. That would give us 50mph wind gusts tomorrow morning which seems reasonable based on the strength of the storm. The NWS has issued a Wind Advisory for tomorrow and scattered power outages are certainly possible. Winds subside tomorrow evening.

The core of the Arctic airmass moves overhead Monday and the chill will definitely be felt across the area. Temps look to barely get to freezing (if that) even under the powerful April sun. Despite the bitter cold temps, winds will subside and thus temps may even feel warmer when compared to the bitter winds of Sunday. Temps won’t be going very far up on Tuesday either and it’s not until Thursday that temps get even back to normal which is around 50.

By tomorrow night, our next clipper will be approaching from the west bringing another chance for snow. This is the upper air pattern for the wee hours of Monday morning showing an unfavorable setup for snow. The two disturbances are separate and fairly weak. However, the trough is tilting slightly negative (NW to SE) at the last minute. This is why I think we at least see a little snow out of this storm. The seeds for the return of Spring can be seen across MT. That storm arrives Thursday into Friday.

The snow from this storm should reach slightly farther north compared to tomorrow’s flakes. Flurries should make it north to around Route 2 or maybe a little north of there. Jackman and points north likely miss out again. The coast and inland points south of Portland likely see steadier snow that adds up to an inch or two. The heavier precip is again to our south over MA and CT where several inches of snow are possible. The main difference compared to Sunday will be the lack of intense winds though there will be some light NE breezes.

The Setup: Late Week

12Z GFS Showing The Setup For The End Of The Week’s Return To Spring. Image Credit: Accuweather

By the end of the week, the pattern will have shifted slightly. Weather features in the mid latitudes (us) can be classified into two basic categories: longwave features and shortwave features. The long wave features can often be picked up by models many days out. The development of a longwave trough would lead to a colder/stormier pattern. Shortwaves are responsible for the individual storms that actually drop the rain/snow. These features are not often resolved well on models many days out hence forecast uncertainty in specific impacts. The longwave pattern for the end of the week features a Western ridge and an Eastern trough, both oriented NW to SE (negatively tilted). The longwave trough in the east is situated to our west which will lead to the development of southerly flow aloft.

This will bring in a feed of tropical moisture into the area. However, it’s up to the individual shortwaves to put the tropical moisture and thus the heavy rain onto a precise location. Where this is remains up for debate. Anywhere in New England including Maine is in play. Should the storm shift farther east, we may be dealing with a snow event. Should it shift farther west, NY would get the heavy rain while a warm and sticky airmass settles into our area.

I’ll have more details on this storm as we get closer. It looks like the track schedule will allow for evening updates this week. We’ll see how that goes, it’s about as unpredictable as the forecast.

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2 thoughts on “From Winter To Spring This Week”

Ron Marchetti here, Jack. Your extended forecasts are a “go to” supplement to NOAA, and your graphics reveal clear visual explanation for the textual narrative. Thanks for this report. Here in Connecticut, I am anticipating a few hours of weather that may be on the edge of the envelope of precedent.